1. Field of the Invention
The present invention relates to a method for producing metal particles and a metal particulate dispersion, and to a method for producing a metal particle-carrying substance. Metal particles are dispersed within a polymer or oligomer membrane. Specific functional groups existing at the terminal ends of the polymer or oligomer and/or in the side chains thereof interact with particles of the metal and/or its oxide to inhibit the aggregation and growth of the particles and cause relatively uniform distribution in the membrane. The membrane can then be dissolved to produce a metal particulate dispersion to which a carrier is added. The unaggregated metal particles are absorbed by the carrier and become fixed on its surface.
2. Background Art
Several conventional methods are known for producing metal particles in a solution or in a gaseous phase. One conventional method of forming particles involves the dissolving of a compound such as chloroauric acid in an aqueous solution followed by the addition of a reducing agent to colloidize the metal ions in the solution. This is problematic, however, because the formed metal particles are unstable (requiring the addition of a stabilizing surfactant) and the solution contains impurities such as the reducing agent.
Conventional methods of forming metal particles in a gaseous phase include (1) depositing particles of a metal on a substrate through vaporization of the metal and peeling of the particles from the substrate, (2) contacting vaporized metal with a surfactant vapor to give a metal colloid, and (3) trapping vaporized metal particles on an oil. There are problems associated with these gas phase methods. In the first method, the particles which are formed cannot be dispersed for any other use. In the second and third methods, the metal particles are difficult to stabilize and tend to aggregate.
Japanese Patent Publication No. 6-99585 discloses another method which consists of melting a polymer material and then rapidly resolidifying it to give a thermodynamically unstable polymer layer on which a metal film is deposited. Particles of the metal or its oxide then disperse throughout the polymer layer as it stabilizes. However, it is difficult to increase the concentration of the dispersed particles.